Ventilators can be employed to evacuate air and other gases from enclosed spaces. Such enclosed spaces can include the roof space or interior of commercial and domestic buildings, shipping containers, portable buildings and sheds, automobiles etc. The air and other gases evacuated can include warm or heated gases, moist gases, gas containing contaminants such as contaminated air or toxic fumes, stale gases (especially air), etc.
Various types of wind and/or motor-driven rotor ventilators, such as those disclosed in AU 654141 or U.S. Pat. No. 6,302,778, are known. Static ventilators (i.e. the provision of a vent) are also known. Problems specific to ventilators that are mounted outside a structure are that they are exposed to all of the elements, such as wind, rain, snow, etc. As ventilators are generally used to vent an enclosed space, they must be able to prevent such elements from entering the enclosed space. Usually, covers or cowls have been required to prevent the elements from entering into the structure through the ventilator. In the case of wind, or wind and motor- (e.g. hybrid), driven ventilators, these covers or cowls have been associated with reducing the air flow, and thus the efficiency, of the ventilator. The covers or cowls screen at least a part of the blades, thereby reducing the area of the blades exposed to the wind, and thus reducing the overall flow of air achievable.
The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the ventilator or ventilator blade as disclosed herein.